A known structure of a fuel cell separator has recesses and convexes formed on respective faces to define a reactive gas flow path on one face and to define a cooling water flow path on the other face. The shapes of the recesses and the convexes affect the power generation efficiency of the fuel cell. There have been no sufficient discussions or studies on the shapes of the recesses and the convexes formed on each separator by taking into account the power generation efficiency of the fuel cell.